ocaml/byterun/minor_gc.c

/***********************************************************************/
/*                                                                     */
/*                           Objective Caml                            */
/*                                                                     */
/*             Damien Doligez, projet Para, INRIA Rocquencourt         */
/*                                                                     */
/*  Copyright 1996 Institut National de Recherche en Informatique et   */
/*  en Automatique.  All rights reserved.  This file is distributed    */
/*  under the terms of the GNU Library General Public License, with    */
/*  the special exception on linking described in file ../LICENSE.     */
/*                                                                     */
/***********************************************************************/

/* $Id$ */

#include <string.h>
#include "config.h"
#include "fail.h"
#include "finalise.h"
#include "gc.h"
#include "gc_ctrl.h"
#include "major_gc.h"
#include "memory.h"
#include "minor_gc.h"
#include "misc.h"
#include "mlvalues.h"
#include "roots.h"
#include "signals.h"

asize_t minor_heap_size;
char *young_start = NULL, *young_end = NULL;
char *young_ptr = NULL, *young_limit = NULL;
static value **ref_table = NULL, **ref_table_end, **ref_table_threshold;
value **ref_table_ptr = NULL, **ref_table_limit;
static asize_t ref_table_size, ref_table_reserve;
int in_minor_collection = 0;

void set_minor_heap_size (asize_t size)
{
  char *new_heap;
  value **new_table;

  Assert (size >= Minor_heap_min);
  Assert (size <= Minor_heap_max);
  Assert (size % sizeof (value) == 0);
  if (young_ptr != young_end) minor_collection ();
                                           Assert (young_ptr == young_end);
  new_heap = (char *) stat_alloc (size);
  if (young_start != NULL){
    stat_free (young_start);
  }
  young_start = new_heap;
  young_end = new_heap + size;
  young_limit = young_start;
  young_ptr = young_end;
  minor_heap_size = size;

  ref_table_size = minor_heap_size / sizeof (value) / 8;
  ref_table_reserve = 256;
  new_table = (value **) stat_alloc ((ref_table_size + ref_table_reserve)
                                     * sizeof (value *));
  if (ref_table != NULL) stat_free (ref_table);
  ref_table = new_table;
  ref_table_ptr = ref_table;
  ref_table_threshold = ref_table + ref_table_size;
  ref_table_limit = ref_table_threshold;
  ref_table_end = ref_table + ref_table_size + ref_table_reserve;
}

static value oldify_todo_list = 0;

/* Note that the tests on the tag depend on the fact that Infix_tag,
   Forward_tag, and No_scan_tag are contiguous. */

void oldify_one (value v, value *p)
{
  value result, field0;
  header_t hd;
  mlsize_t sz, i;
  tag_t tag;

 tail_call:
  if (Is_block (v) && Is_young (v)){
    Assert (Hp_val (v) >= young_ptr);
    hd = Hd_val (v);
    if (hd == 0){         /* If already forwarded */
      *p = Field (v, 0);  /*  then forward pointer is first field. */
    }else{
      tag = Tag_hd (hd);
      if (tag < Infix_tag){
        sz = Wosize_hd (hd);
        result = alloc_shr (sz, tag);
        *p = result;
        field0 = Field (v, 0);
        Hd_val (v) = 0;            /* Set forward flag */
        Field (v, 0) = result;     /*  and forward pointer. */
        if (sz > 1){
          Field (result, 0) = field0;
          Field (result, 1) = oldify_todo_list;    /* Add this block */
          oldify_todo_list = v;                    /*  to the "to do" list. */
	}else{
          Assert (sz == 1);
          p = &Field (result, 0);
	  v = field0;
          goto tail_call;
	}
      }else if (tag >= No_scan_tag){
        sz = Wosize_hd (hd);
        result = alloc_shr (sz, tag);
        for (i = 0; i < sz; i++) Field (result, i) = Field (v, i);
        Hd_val (v) = 0;            /* Set forward flag */
        Field (v, 0) = result;     /*  and forward pointer. */
        *p = result;
      }else if (tag == Infix_tag){
        mlsize_t offset = Infix_offset_hd (hd);
        oldify_one (v - offset, p);   /* This cannot recurse deeper than 1. */
        *p += offset;
      }else{
        Assert (tag == Forward_tag);
        v = Forward_val (v);          /* Follow the forwarding */
        goto tail_call;               /*  then oldify. */
      }
    }
  }else{
    *p = v;
  }
}

/* Finish the work that was put off by oldify_one.
   Note that oldify_one itself is called by oldify_mopup, so we
   have to be careful to remove the first entry from the list before
   oldifying its fields. */
void oldify_mopup (void)
{
  value v, new_v, f;
  mlsize_t i;

  while (oldify_todo_list != 0){
    v = oldify_todo_list;                /* Get the head. */
    Assert (Hd_val (v) == 0);            /* It must be forwarded. */
    new_v = Field (v, 0);                /* Follow forward pointer. */
    oldify_todo_list = Field (new_v, 1); /* Remove from list. */

    f = Field (new_v, 0);
    if (Is_block (f) && Is_young (f)){
      oldify_one (f, &Field (new_v, 0));
    }
    for (i = 1; i < Wosize_val (new_v); i++){
      f = Field (v, i);
      if (Is_block (f) && Is_young (f)){
        oldify_one (f, &Field (new_v, i));
      }else{
        Field (new_v, i) = f;
      }
    }
  }
}

/* Make sure the minor heap is empty by performing a minor collection
   if needed.
*/
void empty_minor_heap (void)
{
  value **r;

  if (young_ptr != young_end){
    in_minor_collection = 1;
    gc_message (0x02, "<", 0);
    oldify_local_roots();
    for (r = ref_table; r < ref_table_ptr; r++) oldify_one (**r, *r);
    oldify_mopup ();
    if (young_ptr < young_limit) young_ptr = young_limit;
    stat_minor_words += Wsize_bsize (young_end - young_ptr);
    young_ptr = young_end;
    ref_table_ptr = ref_table;
    ref_table_limit = ref_table_threshold;
    gc_message (0x02, ">", 0);
    in_minor_collection = 0;
  }
  final_empty_young ();
#ifdef DEBUG
  {
    value *p;
    for (p = (value *) young_start; p < (value *) young_end; ++p){
      *p = Debug_free_minor;
    }
  }
#endif
}

/* Do a minor collection and a slice of major collection, call finalisation
   functions, etc.
   Leave the minor heap empty.
*/
void minor_collection (void)
{
  long prev_alloc_words = allocated_words;

  empty_minor_heap ();

  stat_promoted_words += allocated_words - prev_alloc_words;
  ++ stat_minor_collections;
  major_collection_slice (0);
  force_major_slice = 0;

  final_do_calls ();

  empty_minor_heap ();
}

value check_urgent_gc (value extra_root)
{
  CAMLparam1 (extra_root);
  if (force_major_slice) minor_collection();
  CAMLreturn (extra_root);
}

void realloc_ref_table (void)
{                                 Assert (ref_table_ptr == ref_table_limit);
                                  Assert (ref_table_limit <= ref_table_end);
                            Assert (ref_table_limit >= ref_table_threshold);

  if (ref_table_limit == ref_table_threshold){
    gc_message (0x08, "ref_table threshold crossed\n", 0);
    ref_table_limit = ref_table_end;
    urge_major_slice ();
  }else{ /* This will almost never happen with the bytecode interpreter. */
    asize_t sz;
    asize_t cur_ptr = ref_table_ptr - ref_table;
                                                  Assert (force_major_slice);

    ref_table_size *= 2;
    sz = (ref_table_size + ref_table_reserve) * sizeof (value *);
    gc_message (0x08, "Growing ref_table to %ldk bytes\n", (long) sz / 1024);
    ref_table = (value **) realloc ((char *) ref_table, sz);
    if (ref_table == NULL) fatal_error ("Fatal error: ref_table overflow\n");
    ref_table_end = ref_table + ref_table_size + ref_table_reserve;
    ref_table_threshold = ref_table + ref_table_size;
    ref_table_ptr = ref_table + cur_ptr;
    ref_table_limit = ref_table_end;
  }
}